<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<style>
  *{
    margin: 0;
    padding: 0;
  }
  .f{
    position: relative;
  }
  /*.one,.there{
    width: 100px;
    height: 100px;
    background-color: red;
    float: left;
  }
  .there{
    float: right;
    margin-top: -100px;
  }
  .two{
    margin:0 100px;
    height: 100px;
    background-color: blue;
  }*/
  .one{
    width: 100px;
    height: 100px;
    position: absolute;
    top: 0;
    left: 0;
    background-color: red;
  }
  .there{
    height: 100px;
    width: 100px;
    position: absolute;
    top: 0;
    right: 0;
    background-color: red;
  }
  .two{
    height: 100px;
    margin:0 100px;
    background-color: blue;
  }

</style>
<body>
  <div class="f">
    <div class="one"></div>
    <div class="two">自适应</div>
    <div class="there"></div>
  </div>
</body>
</html>